Lycodon irwini, Naveen & Mirza & Choure & Chandramouli, 2025

Naveen, R. S., Mirza, Zeeshan A., Choure, Girish & Chandramouli, S. R., 2025, A ‘ Crikey’ new snake: An insular Lycodon Fitzinger, 1826 (Squamata, Colubridae) from the Nicobar Archipelago, India, Evolutionary Systematics 9 (2), pp. 221-228 : 221-228

Lycodon irwini sp. nov.

Figs 2 , 3 , 4 , Table 1

Lycodon subcinctus – Harikrishnan et al. (2010).

Lycodon cf. subcinctus – Liu et al. 2023; Nguyen et al. 2024.

Holotype.

DOSMB 05114 ( adult female), collected near Gandhi Nagar , Great Nicobar Island ( 6.810923 ° N, 93.878795 ° E; 140 m asl) on 15 th August 2017 by S. R. Chandramouli .

Paratypes.

One adult female, ZSI /ANRC/T/10643 collected from Govind Nagar, at the 10 km point, along the East-West Road, Great Nicobar and

Other referred material.

One adult female ZSI / ANRC uncatalogued specimen from Galathea Bay, Great Nicobar.

Diagnosis.

A Lycodon characterized by the following characters: body size fairly large, maximum known total length up to 1197 mm, slender; preocular maybe present or absent (present here only in the holotype), loreal touching orbit; dorsal scale rows 17-17 - 15, anterior part of the body with smooth scales and posterior parts with the outermost rows smooth and the remaining rows feebly keeled; ventral scales 223–238; subcaudals 78–94, paired; TaL / TL 0.20–0.23; supralabials 8, with the 3 rd – 5 th touching orbit; postoculars 2 / 2; cloacal plate divided. Dorsum overall in a shade of glossy black, lacking bands and ventrally greyish black with cream ventrolateral ridge.

Comparison.

Lycodon irwini sp nov. can be distinguished from all other members of the L. subcinctus group by the occasional presence of a preocular scale (vs. always absent in L. subcinctus , L. sealei and L. neomaculatus ); pre-frontal not in contact with orbit (vs. in contact in L. subcinctus , L. sealei and L. neomaculatus ); absence of white bands across the dorsal surface (vs. present in L. neomaculatus ). A higher number of ventrals, total 223–238 (vs. 187–208 in L. neomaculatus , 198–211 in L. sealei ); higher number of subcaudals, 78–94 (vs. 59–69 in L. sealei ), TaL / TL 0.20–0.23 (vs. 0.16–0.18 in L. sealei ), sum of ventral and subcaudals 304–330 (vs. 261–274 in L. sealei ).

Description of the holotype

(Fig. 2 , 3 and 4 ). Specimen DOSMB 05114 is in a good state of preservation. The specimen was fixed in a flat coil with its head resting outside the coil and the tail in the centre. The ventral aspect of the specimen bears three longitudinal incisions made to retrieve tissue for molecular analysis and to attain optimum penetration of the fixative and preservative.

Body slender; tail long, gradually tapering to a pointy and enlarged whitish terminal scute; head oblong shaped, longer than wide (Headw / HeadL 0.88), slightly flattened, moderately distinct from the neck; snout elongate, projecting over the lower jaw, rounded in dorsal profile, truncate and slightly depressed in lateral profile with a weak canthus rostralis; nostrils large, positioned dorso-laterally, round in shape; eyes medium with an elliptical and slightly vertical pupil.

Body scalation. Dorsal scale rows 17-17 - 15; anteriorly dorsal scale rows smooth, scale rows feebly keeled at midbody and posteriorly (dorsal scale keels beginning from 68 th ventral scale), except for the outermost row, which is smooth throughout; scales of the vertebral row not enlarged; 226 ventral scales, laterally angulate; 78 subcaudals, paired and laterally angulate; cloacal plate divided.

Head scalation. Rostral sub triangular, wider ( 6.92 mm) than deep ( 3.19 mm), barely visible from above; nasal longer ( 5.36 mm) than high ( 3.19 mm), partially divided by a small suture above nostril; posterior half of nasal subpentagonal, larger than anterior nasal; nasal surrounded by the first two supralabials, rostral, internasal, prefrontal and loreal; internasals paired, in contact with rostral, nasal, and prefrontal, slightly wider ( 3.98 mm) than long ( 3.3 mm); prefrontals paired, longer than internasals, subrectangular, longer ( 6.7 mm) than wide ( 5.62 mm), in contact with internasal, nasal, loreal, eye, and frontal; supraoculars paired, subrectangular shaped, longer than wide, in contact with prefrontal; frontal small, hexagonal, slightly longer than wide (ratio FrontalL / Frontalw 1.05), tapering posteriorly; parietals paired, 12.1 mm long, 6.24 mm at its widest anterior. and longer than frontal; loreal subrectangular, longer ( 4.97 mm) than high ( 2.02 mm), in contact with eye; postoculars 2 / 2, uppermost scale larger than lowermost; temporals 1 AT + 2 PT; 3 + 3 nuchal scales, slightly larger than adjacent dorsal scales, bordering parietals. Supraocular longer ( 4.23 mm) than wide ( 3.12 mm), larger than preocular; preocular deeper ( 1.72 mm) than wide ( 1.24 mm); supralabials 8 / 8, first and second in contact with nasal, second and third in contact with loreal, third and fifth in contact with eye, third supralabial largest; infralabials 9 / 9, first pair in contact, first to fifth in contact with the anterior pair of chin shields; mental subtriangular in ventral profile, wider than long; anterior chin shields longer than posterior shields; posterior chin shields in narrow contact medially, separated by skin tissue along the mental groove.

Coloration in preservative.

Uniformly bluish-black dorsally from head to tail tip. Laterally, it transitions from black to brownish-black; the head ventrally is creamy with dark grey, poorly defined blotches. The ventral cream colouration bleaches onto a few of the supralabial scales, which are partly in a shade of the dorsum head colouration and partly of the ventral. The preventrals are mainly in a shade of cream, with light grey on their posterior borders. The grey colouration deepens in intensity and area on each subsequent ventral scale, and each scale is nearly dark grey to black, with a thin, faint light grey or cream transverse band roughly at mid-length of each ventral scale. The sharp ventrolateral edge is creamish, merging into a longitudinal stripe on either side of the venter.

Variation.

Both paratypes agree well in general morphology and coloration. Morphometric and meristic variation is documented in Table 1 .

Etymology.

The specific epithet is a patronym honouring the late Stephen Robert Irwin ( 22 February 1962 –1964 September 2006), the renowned Australian zookeeper, conservationist, television personality, and wildlife educator. His passion and dedication to wildlife education and conservation have inspired naturalists and conservationists worldwide, including the authors of this paper.

Natural history, distribution, and conservation status.

The holotype was collected in a moist evergreen forest, where the snake was observed on a road. Another specimen ( ZSI, uncatalogued was also collected from a moist evergreen forest (pers. comm. G. Gokulakrishnan )). Another uncollected adult female was observed by RSN crossing the East-West Road near Govind Nagar, in a similar moist evergreen forest habitat. Currently, only four records of this species are known, three of which are based on collected specimens described in this study. All known specimens are from Great Nicobar Island, and despite targeted surveys on other Nicobar Islands, the species has not been recorded elsewhere, suggesting it is likely endemic to Great Nicobar Island. Its rarity in field encounters implies it may be naturally scarce, highly cryptic, and possibly confined to the island’s evergreen forests. Considering this, along with potential threats from ongoing development activities that could impact its only known habitat, we recommend assessing the species as Endangered on the IUCN Red List under criteria B 1 ab (iii); C 2 a (ii).

Figures

Figure 2. Lycodon iriwini sp. nov., adult female holotype (Voucher no. DOSMB 05114). a. Dorsal view; b. Ventral view. Scale bars: 10 mm.

Figure 3. Lycodon iriwini sp. nov., adult female holotype (Voucher no. DOSMB 05114), head views. a. Dorsal aspect; b. Ventral aspect; c. Right lateral aspect; d. Left lateral aspect.

Figure 4. Lycodon irwini sp. nov., dorsolateral view of an adult female in life.